Spectral Performance and Calibration of the Suomi NPP OMPS Nadir Profiler Sensor Earth and Space Science

The Ozone Mapping and Profiler Suite (OMPS) is one of five instruments on board the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite. As part of OMPS, the Nadir Profiler (NP) spectrometer measures Earth's albedo in ultraviolet wavelengths from 250 to 310nm to profile Earth atmospheric ozone concentration. Since launch in 2011, many changes in the NP radiometric and spectrometric calibration have been made to improve sensor data quality. The most challenging issue is to characterize instrument on-orbit spectral calibration and to maintain a stable spectral performance to meet sensor design criteria. Validation of the NP sensor data found an average of 3-5% error in the sensor albedo measurements that exceeded 2% requirement, creating 1-2% uncertainty in ozone profile. Data analysis attributes the error to prelaunch calibration uncertainty, ground-to-orbit dichroic changes, and on-orbit detector wavelength registration drifts. A recent update of calibration significantly improved spectral wavelength knowledge as well as the accuracy of the measured solar spectra. As a result, the wavelength-dependent albedo error is significantly reduced and generally meets the radiometric uncertainty requirement of 2%.